Small limb is bitternut or pignut hickory for sure. I split all my wood by hand so I consider hickory to be about the toughest to split. For a straight grained piece when hit with a maul it pops open pretty easy but all those little fibers hold the splits together. You can't pull it apart by hand so you have to keep driving the wedge into the log or use an ax to cut thru all the little fibers sticking together. Of course if you put it on a splitter it will bust pretty easy but you have to use the full stroke to cut the fibers or pull the splits apart with a wide wedge. This is one of the reasons that hickory is used for handles on axes, hammers, shovels etc. It holds together better than almost any other wood. It is also among the best wood out there for BTU's and also has some really good smoke flavor for making BBQ. I tend to use the white wood for making ax handles, the heart wood for the smoker, and every thing else goes into the wood stove. Of course bugs love hickory too so I try to burn it 1 year after cutting just to eliminate the piles of dust that boring beetles leave. It also pops and throws sparks a lot too so many people don't like it in an open fire place. I think it is the bugs that really make it pop so bad. I have a real love/ hate relationship with hickory. Love the heat, smell, durability for handles, but hate having to split it, all the dust the bugs leave, all the popping when I open the stove, and hauling the weight of the green stuff.